Determining the diffusion coefficient of Ca(OH)2in concrete with age in an artificial seawater environment

Abstract

Concrete structures exposed to marine environments, which contain high levels of Cl-and SO42-ions, accelerate the diffusion process of calcium hydroxide (Ca(OH)2), particularly in tidal zones due to the combined effects of carbonation and mechanical erosion from waves. The characteristic feature of the diffusion process of calcium hydroxide in concrete within marine environments is the diffusion coefficient of calcium hydroxide (k). This study involves an experiment to determine the calcium hydroxide content in concrete submerged in water containing 5% NaCl. Experimental results were combined with the solution of the uncertainty diffusion problem to determine the diffusion coefficient of calcium hydroxide in concrete samples with a standard compressive strength of 28.7MPa. Comparisons with previous studies indicate that the diffusion coefficient of calcium hydroxide in concrete varies depending on the type of concrete. Additionally, the study reveals that the diffusion coefficient of calcium hydroxide in conventional concrete increases with prolonged immersion time. In previous studies, for high-strength concrete types using active mineral additives, this coefficient decreases over time. Thisstudyindicates that the different pore structures between conventional and high-strength concretelead to different effects of permeability on these concrete types, resulting in varying trends of calcium hydroxide diffusion over time